This invention relates generally to capacitors and specifically to metal cased electrolytic capacitors having an epoxy sealant.
Flat pack electrolytic capacitors are well known in the art as exemplified by U.S. Pat. No. Des. 353,575, issued Dec. 20, 1994 and assigned to the assignee of the present invention. While the design patent does not indicate the manner of construction of the flat pack capacitor, in practice, an open-ended aluminum case is sealed with a welded end cap that includes an electrolyte fill hole (and connecting leads for the capacitor in the case). Welding the case and cover after installation of the electrolyte often leads to boiling away of the electrolyte with consequent deterioration in the life of the capacitor. Filling the case with electrolyte after welding eliminates the above-mentioned problem, but requires that an elastic plug seal or the like be installed in the fill hole and further that the entire end cap (which is dish-shaped) be filled with an epoxy sealant. The present invention utilizes low cost off-the-shelf parts to provide a seal mechanism for the fill hole to preclude leakage of electrolyte under normal operating conditions. As is common practice vents are provided in the case to permit any gases that may be generated under abnormal operating conditions to be safely vented to the atmosphere. With the invention, the need for the epoxy sealant is obviated. The method of manufacture also lends itself to automation.
In accordance with the invention, an electrolytic flat pack capacitor is constructed by welding an end cap to a case containing the capacitor and filling the case with an electrolyte via a fill hole in the end cap. A seal mechanism is installed in the fill hole, which seal mechanism precludes leakage of electrolyte under normal operating conditions in the preferred embodiment of the invention, the seal mechanism comprises an elastic O ring that is controllably compressed by a closed end pop rivet.